Investigation of flow and heat transfer behavior of integrated pin fin-aluminum foam heat sink

Abstract

• A novel aluminium foam heat sink (AFHS) consisting of pin fin inserts is proposed. • The developed mathematical model is validated with experimental data. • Thermo-hydraulic characteristics of proposed heat sinks are numerically studied. • Pin fin inserts lead to an enhancement on the heat removal capability of AFHS. • Pressure drop along the flow direction increases with pin fin insertion into AFHS. With the rapid development in the electronics industry, the thermal management of high power density electronic products (HPDEPs) has become very important and requires innovative heat removal technologies. In this study, an integrated heat sink (IHS) fabricated by combining aluminum foam and pin-finned heat sink configurations that are frequently used in the cooling of electronic products has been proposed as an effective solution for the thermal management of HPDEPs. The heat removal and pressure drop characteristics of the IHS were numerically investigated for its various design conditions such as the length/height ratio ( L/H ), fin profile, fin/foam height ratio ( H fin /H foam ), and heat sink/fin volume ratio ( V hs /V f ) over the range of Reynolds ( Re Dh ) number from 500 to 3500 by using the COMSOL Multiphysics v5.4. Before the numerical study was performed, to verify the outcomes of the developed simulation models, some of the IHS subjected to the numerical study were fabricated and their pressure drop and heat removal performances were experimentally examined in the range of Re Dh from 596 to 3551. As a result of the study, it was found that the thermal contact resistance ( TCR ) between the IHS and the heated surface has a greater effect on the Nusselt ( Nu ) number compared to the TCR between the solid fins and aluminum foam. The in-line or staggered arrangement of pin fins inside the aluminum foam did not lead to any significant difference in the overall performance of investigated IHS. For all the IHS examined, an increase in Re Dh results in a similar increase in the Nu and ΔP along the flow direction. In general, the most efficient IHS among the investigated ones in terms of the H fin /H foam ratio is the IHS with half-length fins, H fin /H foam =15/30. Average values of thermal performance factor ( ƞ) of the IHS with H fin /H foam ratio of 15/30 in in-line and staggered arrangement over the Re Dh number studied are 1.3 and 1.25 times higher relative to IHS with H fin /H foam ratio of 30/15. For a fixed number of fins, η of the IHS with fins of 4mm diameter is superior up to Re Dh =2000, after which, the situation varies in favor of the 8mm solid finned aluminum foam heat sink. Increasing the fin diameter from 4mm to 12mm in both fin configurations worsens the average value of ƞ by 10%. For a constant fin diameter, IHSs with 9 fins in in-line and 8 fins in staggered configuration have the highest ƞ when the Re Dh is greater than 2500 and 2000, respectively. Among the fin profiles examined, the IHS with elliptical fins is found to have the highest η , with a value of 1.24, at Re Dh =3500.